\documentclass[tikz,border=10pt]{standalone}
\usepackage{tikz}
\usetikzlibrary {scopes}
\usetikzlibrary{positioning}
\usetikzlibrary{arrows.meta}
\begin{document}

\begin{tikzpicture}[scale=3]
    \node[draw,scale=.5,circle, label={below:$ru_{i-1,j}$} ](a) at (0,0){};
    \node[draw,scale=.5,circle, label={below:$(1-2r)u_{i,j}$}](b) at (1,0){};
    \node[draw,scale=.5,circle, label={below:$ru_{i+1,j}$}](c) at (2,0){};
    \node[draw,scale=.5,circle, label={above:$u_{i,j+1}$}](d) at (1,.5){};
    \draw (a)--(b) --(c);
    \draw[densely dashed] (b) --(d);

\end{tikzpicture}

\end{document}
